MongoLockProvider (Carrot Task Queue 2.0.2 API)

java.lang.Object
- cn.boboweike.carrot.lock.nosql.MongoLockProvider

All Implemented Interfaces:

LockProvider
```
public class MongoLockProvider
extends Object
implements LockProvider
```
Adapted from https://github.com/lukas-krecan/ShedLock/blob/master/providers/mongo/shedlock-provider-mongo/src/main/java/net/javacrumbs/shedlock/provider/mongo/MongoLockProvider.java Distributed lock using MongoDB >= 2.6. Requires mongo-java-driver > 3.4.0
It uses a collection that contains documents like this:
```
 {
    "_id" : "lock name",
    "lockUntil" : ISODate("2017-01-07T16:52:04.071Z"),
    "lockedAt" : ISODate("2017-01-07T16:52:03.932Z"),
    "lockedBy" : "host name"
 }
 
```
lockedAt and lockedBy are just for troubleshooting and are not read by the code
1. Attempts to insert a new lock record. As an optimization, we keep in-memory track of created lock records. If the record has been inserted, returns lock.
2. We will try to update lock record using filter _id == name AND lock_until <= now
3. If the update succeeded (1 updated document), we have the lock. If the update failed (0 updated documents) somebody else holds the lock
4. When unlocking, lock_until is set to now.

Field Summary
- Fields inherited from interface cn.boboweike.carrot.lock.LockProvider
  LOCK_UNTIL, LOCKED_AT, LOCKED_BY

Constructor Summary

Constructors
Constructor Description

MongoLockProvider(com.mongodb.client.MongoCollection<org.bson.Document> collection)
Uses Mongo to coordinate locks

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`extend(String name, int durationInSeconds, String lockedBy)`
`boolean`	`lock(String name, int durationInSeconds, String lockedBy)`
`boolean`	`unlock(String name)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- MongoLockProvider
```
public MongoLockProvider(com.mongodb.client.MongoCollection<org.bson.Document> collection)
```
  Uses Mongo to coordinate locks
  
  Parameters:
  
  collection - Mongo collection to be used

Method Detail

lock

public boolean lock(String name,
                    int durationInSeconds,
                    String lockedBy)

Specified by:: lock in interface LockProvider

extend

public boolean extend(String name,
                      int durationInSeconds,
                      String lockedBy)

Specified by:: extend in interface LockProvider

unlock
```
public boolean unlock(String name)
```
Specified by:

unlock in interface LockProvider